The present invention relates to improvements in printing systems. More particularly this invention relates to a system for enabling the execution of control functions related to printing with a minimum of adverse effect on the printing process.
Systems exist which control the printing of information received from a transmission line. The printing system recognizes the coincidence of input characters received from the transmission line or data source and the instantaneous column position of printing or type characters to enable the concurrent printout of a plurality of information corresponding to the input characters at the proper position on a print line. Such printing systems utilize storage units for storing the input characters until the comparison with print characters can be made. If for some reason printout is delayed and input information is not accordingly delayed, the storage unit capacity is soon reached and data is lost. Such a problem is presented at the end of each print line when the line change operation takes place. Line change takes a finite amount of time and printing must cease during this time. One procedure for accommodating the line feed data in printing is to program the transmission line from which data is received to supply fill characters. That is, characters which are not to be printed and therefore not to be stored in the print character memory are provided to take up time for the line feed operation to take place. Fill characters therefore are intended to delay the intelligence being transmitted so that no intelligence is lost during the line feed operation.
The difficulty with using fill characters to accommodate line feed is that additional source programming is necessary to provide the remote source of information with as many fill characters as are needed. In addition, fill characters contain no intelligence and only serve to take up transmission time resulting in less efficient transmission of intelligence. Also because fill characters are being transmitted when line change is taking place, no subsequent line information may be put into the memory and printer throughout, i.e. the rate of printing intelligence, is reduced.